Constant velocity joint

ABSTRACT

A constant velocity joint that enables a wide continuous range of shaft angles, being robust throughout this range. 
     It reduces the inertia torque loads on the shafts. 
     The best efficiency, and the least wear, is with the shafts at a straight line. 
     It fits even to driveshafts of cars wherein the maximum angle is near 50 degrees.

The closest prior art is the patent U.S. Pat. No. 7,442,126, FIGS. 1, 2,4, wherein a first shaft yoke, a second shaft yoke and a control yokeare pivotally mounted to each other to pivot about a common axis.

The first shaft yoke is pivotally mounted on a first shaft with thepivot axis perpendicular to the first shaft rotation axis, the secondshaft yoke is pivotally mounted on “a second shaft boss having an axisnormal to said second shaft rotation axis”, as disclosed in the firstclaim of the closest prior art patent.

The control yoke is pivotally mounted to the center of a sphericalpantograph, or control, mechanism to keep the common axis at the rightorientation and the transmission ratio at 1:1. The one end of thecontrol mechanism pivots about an oblique pin of the first shaft, theother end of the control mechanism pivots about an oblique pin of thesecond shaft.

The spherical pantograph mechanism comprises six articulated “links”(they actually act as six articulated yokes), with all pivot axesintersecting at the center of the joint.

In total the closest prior art CVJ, or TCVJ (Thompson Constant VelocityJoint) comprises nine yokes of all kinds: a triad that makes the mainwork and comprises a first shaft yoke, a second shaft yoke and a controlyoke, and six more links that constitute the control mechanism thatkeeps the common axis at the right orientation.

Besides transferring torque from the one shaft to the other, themechanism is capable for transferring axial load without needing thrustbearings, at least in the case the two shafts are in a straight line.When the two shafts are at an angle, thrust loads on the joint bearingsresult, just like in the conventional Cardan joint. The thrust loads areproportional to the axial load transferred by the joint and depend onthe angle between the shafts and on the rotation angle of the shafts.

A disadvantage of the closest prior art (or TCVJ) coupling is that itcannot reliably operate with the two shafts at a straight line. Aminimum angle of 2 degrees between the two shafts is required, otherwise“the parts of the coupling rapidly wear” according the inventor andmaker of the TCVJ (quote from his web sitehttp://www.thompsoncouplings.com, under the title Special Instructions:“Continuous operation of the TCVJ coupling at 0 degrees is notrecommended as this will cause wear on bearings and cause damage to thecoupling. For maximum efficiency and life of the TCVJ coupling, aminimum operating angle of 2.0 degrees is recommended.”)

With the two shafts at a straight line, the first shaft yoke, the secondshaft yoke and the control yoke stay coplanar, which means their normalto the common axis pivots are in a straight line perpendicular to both,the common axis and the straight line along the two shafts. The supportof the control yoke becomes problematic and the result is the rapid wearof the bearings.

With the two shafts at an angle, the TCVJ transmits the torque of thedriving shaft to the driven shaft and loads the control yoke with arespective idle torque. In order the control mechanism to support thecontrol yoke and to receive the idle torque, it bends slightly at onedirection. After the shaft angle wherein the two shaft yokes becomecoplanar, the idle torque changes direction and the control mechanismbends at the opposite direction. That is, in order to provide to thecontrol yoke the necessary support, the control mechanism bends at onedirection leaving its geometrically correct position, and when thenecessary support changes direction, the control mechanism bends at theopposite direction, leaving again its geometrically correct position.

Geometrically the TCVJ coupling is perfect, but the flexibility of theparts and the inevitable lash of the bearings spoil the geometry. Forinstance, with just 0.02 mm lash in every bearing of the sphericalpantograph of the TCVJ, and with the shafts of the coupling at onedegree angle, the spherical pantograph performs an oscillating motionbending, like a chord, initially at one direction until it is adequatelybend away to provide the necessary support/force to the control yoke,then it bends at the opposite direction until it is adequately bend awayto provide the necessary force to the control yoke at the otherdirection, and so on.

The impact loads of this motion combined with the absence of rotation ofthe pin of the bearing relative to the rest bearing (because of thesmall angle between the shafts) spoils the lubrication of the bearingand causes the fatigue of the bearings.

Another disadvantage of the TCVJ is the moment of inertia of the controlyoke that loads the driving and the driven system with an inertia torqueand torsional vibrations. With the two shafts rotating at constantangular velocity, the control yoke rotates at a varying angularvelocity. The bigger the angle between the shafts, the wider thevariation of the angular velocity of the control yoke. The control yokeaccelerates, absorbing energy from the shafts, and then decelerates,delivering energy to the shafts, two times per shaft rotation.

It is an object of the present invention to address the abovedisadvantages. Accordingly, there is provided a constant velocity jointas defined in the appended claims.

FIG. 1 shows the state of the art CVJ, or TCVJ.

FIG. 2 shows what FIG. 1 after the removal of the control mechanism,which is shown at left.

FIG. 3 shows a first embodiment.

FIG. 4 shows the main mechanism of the prior art partly disassembled.

FIG. 5 shows the main mechanism of the first embodiment partlydisassembled for comparison to the state of the art of FIG. 4.

FIG. 6 shows some parts and subassemblies of a second embodiment.

FIG. 7 shows the second embodiment complete.

FIG. 8 shows what FIG. 7, with the two shafts of the mechanism moved atleft and right.

FIG. 9 shows what FIG. 8 with a pair of shaft yokes and the respectivecontrol yoke assembled onto the two shafts.

FIG. 10 shows what FIG. 7 partly disassembled. In the middle it is shownthe assembly of the three control yokes, which is also shown at topdisassembled.

FIG. 11 shows the mechanism of FIG. 7 from two different viewpoints. Thesimultaneous watching of the two images makes the details clear.

FIG. 12 shows a third embodiment.

FIG. 13 shows the third embodiment partly disassembled.

FIG. 14 shows the third embodiment partly disassembled.

FIG. 15 shows the left shaft of the third embodiment, its three shaftyokes and the three control yokes.

FIG. 16 shows three subassemblies of the third embodiment eachcomprising a control yoke and the pair of shaft yokes it connects.

FIG. 17 shows, from two different viewpoints, the third embodimentpartly disassembled. The simultaneous watching of the left and rightimages makes the details clear.

FIG. 18 shows a fourth embodiment.

FIG. 19 shows the main mechanism of the prior art partly disassembled.

FIG. 20 shows the main mechanism of the fourth embodiment partlydisassembled for comparison to the prior art of FIG. 19. The A1 axis isnear, but not exactly, perpendicular to the first rotation axis X1.

FIG. 21 shows a fifth embodiment. The A1 to X1 angle is 87 degrees;smaller or bigger angles can be used, too.

FIG. 22 shows the fifth embodiment disassembled.

FIG. 23 shows the fifth embodiment from a different viewpoint.

FIG. 24 shows the fifth embodiment disassembled, from another viewpoint.

Among the objects of this invention is to disclose a CVJ that:

interconnects two shafts with a strict 1:1 transmission ratio for a widerange of angles between the two shafts,

is capable to transmit heavy axial loads,

needs not thrust bearings others than the conventional universal jointbearings;

is reliable throughout the complete range of angles between the shafts,the case with the two shafts at a straight line included,

avoids the condition wherein the shaft yokes are coplanar,

splits the torque among all the peripheral bearings,

avoids the weak control mechanism,

substantially decreases the inertia vibrations,

is capable for a wide range of shaft angles, even wider than −50 to +50degrees.

In a first embodiment, FIGS. 3 and 5, the CVJ resembles to that of theclosest prior art.

Two shaft yokes and a control yoke are pivotally mounted to each otherso that they pivot about a common axis. The first shaft yoke ispivotally mounted on the first shaft with the first shaft pivot axis A1substantially oblique relative to the rotation axis X1 of the firstshaft. The second basic cross is pivotally mounted on an oblique boss ofa second shaft, with the second shaft pivot axis A2 substantiallyoblique relative to the rotation axis X2 of the second shaft. The A1 andthe A2 axes remain symmetrical about the bisecting plane of the anglebetween the rotation axes X1 and X2 of the two shafts by means of thecontrol yoke which is pivotally mounted on the center of a sphericalpantograph, or control, mechanism. The one end of the control mechanismpivots on an oblique pin of the first shaft, the other end of thecontrol mechanism pivots on an oblique pin of the second shaft.

The shaft yokes remain permanently not coplanar, avoiding theunstable/unreliable condition of the closest prior art. For as long asthe torque transferred remains exclusively positive (or exclusivelynegative), the control mechanism is permanently loaded at the samedirection so that it bends slightly at one direction only and needs notto pass from its “unstable condition” twice per shaft rotation. This waythe CVJ operates reliably and efficiently even when the two shafts arenear, or exactly, a straight line.

Just like the TCVJ, the CVJ of the first embodiment consists of a mainmechanism (the two shaft yokes and the control yoke) to withstand theloads, and of a secondary mechanism for the control.

In comparison to the TCVJ, the maximum idle torque that loads thecontrol mechanism of the CVJ of the first embodiment is heavier,decreasing the capacity of the joint for a given control mechanism.Besides, in case of axial load, stronger thrust loads are generated.

The next embodiments solve these disadvantages.

In a second embodiment, FIGS. 6 to 11, the CVJ comprises threemechanisms like the main mechanism of the first embodiment (the boss ofthe second shaft is replaced by a fork like that of the first shaft),and without secondary mechanism at all. The number of yokes of all kindsremains 9 as in the closest prior art. The three mechanisms are arrangedat 120 degrees from each other. The three control yokes, which areactually control crosses, are pivotally mounted to each other to pivotabout a common axis Z.

Instead of “dedicating” some parts to the control of the mechanism, andsome others to the transfer of the torque and of the axial load, now allparts contribute to both, the control of the mechanism and the transferof the torque and axial loads.

In a third embodiment, FIGS. 12 to 17, the shaft yokes of the secondembodiment are forks. The forks are mounted to the shafts by double, orlonger, bearings. This arrangement enables wider angles between the twoshafts, making the joint appropriate for even wider angles between theshafts. For the assembly of the mechanism, one of the control yokescomprises two pieces secured to each other to form a cross; with the onepiece being a pin that inserts into a hole of the other piece. Above andbelow the single piece cross of FIG. 15, it is shown the version whereinthe cross comprises two pieces, the one secured to the other. The pin ofthe two pieces cross is assembled last, “locking” the joint.

For the minimization of the inertia torque, for simplicity, forsymmetry, for the minimization of the maximum loads on the parts and forequal distribution of the loads among the peripheral bearings, the shaftyokes are spaced out at 120 degrees around their shaft axis, while theyare arranged at the same angle, about 50 degrees in this specificrealization, from the rotation axis of their shaft.

With conventional universal joint bearings, like those used in the TCVJof the closest prior art, the mechanisms of the second and thirdembodiments can take similar axial loads with the TCVJ.

For instance: with the two shafts of the CVJ of the third embodiment ata straight line, the axial load applied on the first shaft passesthrough the three shaft yokes of the first shaft, to the assembly of thethree control yokes; then it passes to the second shaft through itsthree shaft yokes. Conventional universal joint bearings keep the shaftyokes in place, so that the actual center of the joint remains at thegeometrical centers of the joint without significant thrust loads on thebearings, just like in the TCVJ of the closest prior art.

In case of axial loading with the shafts at an angle, the universaljoint bearings take the resulting thrust loads, just like the universaljoint bearings of the TCVJ take the resulting thrust loads.

Instead of the single and heavy control yoke of the TCVJ, the second andthird embodiments of this invention include three lighter members(crosses) arranged around the mechanism (typically at 120 degrees apartfrom each other when the shafts are at a straight line). The total idleenergy that oscillates to-and-fro the shafts and the three controlyokes, to make them move as the mechanism commands, is smaller becausewhen some of them absorb energy to accelerate, some other return energyto decelerate making the total inertia torque on the shafts smaller(just like a six cylinder even firing engine has smaller inertia torquesthan a four in line even firing engine).

In a fourth embodiment, FIGS. 18 and 20, the CVJ comprises:

a first shaft rotating about a first rotation axis X1;

a second shaft rotating about a second rotation axis X2, the firstrotation axis X1 and the second rotation axis X2 intersect at the centerof the joint which is a fixed point with respect to the first shaft, anda fixed point with respect to the second shaft;

a triad of yokes comprising a control yoke, a first shaft yoke and asecond shaft yoke,

the first shaft yoke being pivotally mounted on the first shaft with therespective first pivot axis A1 passing through the center of the joint,the first pivot axis A1 is near, but not exactly, perpendicular to thefirst rotation axis X1, the second shaft yoke being pivotally mounted onthe second shaft with the respective second pivot axis A2 passingthrough the center of the joint and being oblique to the second rotationaxis X2, the angle between the first pivot axis A1 and the firstrotation axis X1 equals to the angle between the second pivot axis A2and the second rotation axis X2, the three yokes of the triad of yokesare pivotally mounted to each other to pivot about a common axis passingthough the center of the joint;

a set of auxiliary yokes, the set of auxiliary yokes constitutes aspherical pantograph mechanism, the one end of the spherical pantographmechanism is pivotally mounted on an oblique pin of the first shaft, theother end of the spherical pantograph mechanism is pivotally mounted onan oblique pin of the second shaft, the control yoke is pivotallysupported at the center of the spherical pantograph mechanism so thatthe transmission ratio is strictly 1:1.

An angle of 89 degrees between the pivot axis A1 and the rotation axisX1 (which means the A1 is almost perpendicular to the X1), and an equalangle of 89 degrees between the pivot axis A2 and the rotation axis X2,result in an angle of 2 degrees between the pivot axes A1 and A2 in thecase the two shafts operate at a straight line. Instead of limiting theavailable angle range of the TCVJ to angles above 2 degrees, i.e. toangles wherein the three yokes do not stay “almost coplanar”, now themechanism itself avoids the condition at which the three yokes remainpermanently “almost coplanar”.

With the pivot axis A1 “almost” perpendicular to the rotation axis X1,the thrust loads on the bearings of the coupling remain small.

Lubrication and wear of the bearings of the fourth embodiment: If f isthe angle between the pivot axes A1 and A2 when the two shafts are at astraight line, then, with the shafts at any angle from zero to f, aconstant direction incoming torque loads the spherical pantographmechanism permanently at the same direction throughout the entire shaftrotation (i.e. the spherical pantograph avoids to bend at one direction,then to straighten and then to bend at the opposite direction); thebearings of the spherical pantograph either do not rotate at all (caseof shafts at a straight line) or undergo a slight angular oscillation;this is the case in the TCVJ coupling, too, when it operates with theshafts at, or nearly, a straight line. But in the present CVJ, the pinof any bearing of the pantograph mechanism abuts constantly on the sameside of the bearing eliminating the wear. In comparison, the pin of anybearing of the spherical pantograph mechanism of the TCVJ goes from sideto side of the bearing, hitting the surface, cleaning the bearingsurface from the lubricant and finally wearing the bearing.

For angles bigger than f, the spherical pantograph bearings of thepresent CVJ rotate and lubricate normally, avoiding the wear.

Even a slight inclination (like 0.5, 1.0, 2.0, 3.0 degrees) of the pivotaxis A1 from the normal to the rotation axis X1, at the center of thejoint, plane, substantially changes the way the joint operates: thelubrication of the bearings improves, the wear of the joint reduces andthe joint gets rid of a range of shaft angles around zero wherein thefatigue stressing makes its durability suffer.

With the nearly, but not exactly, perpendicular “pivot to rotation”axes, the constant velocity joint of the fourth embodiment avoids thetwo critical conditions to take place (to occur) at the same time: thebearing-pins do not actually rotate inside their bearings and thespherical pantograph mechanism bends from side to side to provide thenecessary support to the control yoke.

In a fifth embodiment, FIGS. 21 to 24, an oblique fork substitutes theoblique boss of the fourth embodiment, increasing the torque capacity ofthe coupling. In the FIGS. 21 to 24 the angle between the pivot axis A1and the rotation axis X1 is 87 degrees; other angles can be used, too.The first shaft yoke, the second shaft yoke and the control yoke pivotabout the common axis C, FIG. 24.

Animations of the abovementioned CVJ mechanisms are available at:http://www.pattakon.com/pattakonPatDAN.htm

Although the invention has been described and illustrated in detail, thespirit and scope of the present invention are to be limited only by theterms of the appended claims.

1. A constant velocity joint comprising at least: a first shaft rotatingabout a first rotation axis (X1); a second shaft rotating about a secondrotation axis (X2), the first rotation axis (X1) and the second rotationaxis (X2) intersect at the center of the joint which is a point fixedrelative to the first and second shafts; a first triad of yokescomprising a first triad control yoke, a first triad first shaft yokeand a first triad second shaft yoke, the first triad first shaft yokebeing pivotally mounted on the first shaft with the respective firstshaft first pivot axis (A1) passing through the center of the joint andbeing substantially oblique to the first rotation axis (X1), the firsttriad second shaft yoke being pivotally mounted on the second shaft withthe respective second shaft first pivot axis (A2) passing through thecenter of the joint and being substantially oblique to the secondrotation axis (X2), the angle between the first shaft first pivot axis(A1) and the first rotation axis (X1) equals the angle between thesecond shaft first pivot axis (A2) and the second rotation axis (X2),the three yokes of the first triad of yokes are pivotally mounted toeach other to pivot about a first common axis (C) passing though thecenter of the joint; a set of additional pivotally mounted yokes thatkeeps the first triad control yoke at the right orientation, the pivotaxes of the pivotally mounted yokes of the set of additional pivotallymounted yokes passing through the center of the joint.
 2. A constantvelocity joint according claim 1 wherein: said set of additionalpivotally mounted yokes comprising a second triad of yokes and a thirdtriad of yokes; the second triad of yokes comprising a second triadcontrol yoke, a second triad first shaft yoke and a second triad secondshaft yoke, the second triad first shaft yoke being pivotally mounted onthe first shaft with the respective first shaft second pivot axis (A1′)passing through the center of the joint and being substantially obliqueto the first rotation axis (X1), the second triad second shaft yokebeing pivotally mounted on the second shaft with the respective secondshaft second pivot axis (A2′) passing through the center of the jointand being substantially oblique to the second rotation axis (X2), theangle between the first shaft second pivot axis (A1′) and the firstrotation axis (X1) equals the angle between the second shaft secondpivot axis (A2′) and the second rotation axis (X2), the three yokes ofthe second triad of yokes are pivotally mounted to each other to pivotabout a second common axis (C′) passing though the center of the joint;the third triad of yokes comprising a third triad control yoke, a thirdtriad first shaft yoke and a third triad second shaft yoke, the thirdtriad first shaft yoke being pivotally mounted on the first shaft withthe respective first shaft third pivot axis (A1″) passing through thecenter of the joint and being substantially oblique to the firstrotation axis (X1), the third triad second shaft yoke being pivotallymounted on the second shaft with the respective second shaft third pivotaxis (A2″) passing through the center of the joint and beingsubstantially oblique to the second rotation axis (X2), the anglebetween the first shaft third pivot axis (A1″) and the first rotationaxis (X1) equals the angle between the second shaft third pivot axis(A2″) and the second rotation axis (X2), the three yokes of the thirdtriad of yokes are pivotally mounted to each other to pivot about athird common axis (C″) passing though the center of the joint; the firsttriad control yoke, the second triad control yoke and the third triadcontrol yoke are pivotally mounted to each other to pivot about a commonaxis (Z) perpendicular to the first common axis (C), to the secondcommon axis (C′) and to the third common axis (C″) at the center of thejoint.
 3. A constant velocity joint according claim 1 wherein: said setof additional pivotally mounted yokes comprising a second triad of yokesand a third triad of yokes; the second triad of yokes comprising asecond triad control yoke, a second triad first shaft yoke and a secondtriad second shaft yoke, the second triad first shaft yoke beingpivotally mounted on the first shaft with the respective first shaftsecond pivot axis (A1′) passing through the center of the joint andbeing substantially oblique to the first rotation axis (X1), the secondtriad second shaft yoke being pivotally mounted on the second shaft withthe respective second shaft second pivot axis (A2′) passing through thecenter of the joint and being substantially oblique to the secondrotation axis (X2), the angle between the first shaft second pivot axis(A1′) and the first rotation axis (X1) equals the angle between thesecond shaft second pivot axis (A2′) and the second rotation axis (X2),the three yokes of the second triad of yokes are pivotally mounted toeach other to pivot about a second common axis (C′) passing though thecenter of the joint; the third triad of yokes comprising a third triadcontrol yoke, a third triad first shaft yoke and a third triad secondshaft yoke, the third triad first shaft yoke being pivotally mounted onthe first shaft with the respective first shaft third pivot axis (A1″)passing through the center of the joint and being substantially obliqueto the first rotation axis (X1), the third triad second shaft yoke beingpivotally mounted on the second shaft with the respective second shaftthird pivot axis (A2″) passing through the center of the joint and beingsubstantially oblique to the second rotation axis (X2), the anglebetween the first shaft third pivot axis (A1″) and the first rotationaxis (X1) equals the angle between the second shaft third pivot axis(A2″) and the second rotation axis (X2), the three yokes of the thirdtriad of yokes are pivotally mounted to each other to pivot about athird common axis (C″) passing though the center of the joint; the firsttriad control yoke, the second triad control yoke and the third triadcontrol yoke are pivotally mounted to each other to pivot about a commonaxis (Z) perpendicular to the first common axis (C), to the secondcommon axis (C′) and to the third common axis (C″) at the center of thejoint, the first shaft first pivot axis (A1) and the second shaft firstpivot axis (A2) being substantially perpendicular to the first commonaxis (C), the first shaft second pivot axis (A1′) and the second shaftsecond pivot axis (A2′) being substantially perpendicular to the secondcommon axis (C′), the first shaft third pivot axis (A1″) and the secondshaft third pivot axis (A2″) being substantially perpendicular to thethird common axis (C″).
 4. A constant velocity joint according claim 1wherein: said set of additional pivotally mounted yokes comprising asecond triad of yokes and a third triad of yokes; the second triad ofyokes comprising a second triad control yoke, a second triad first shaftyoke and a second triad second shaft yoke, the second triad first shaftyoke being pivotally mounted on the first shaft with the respectivefirst shaft second pivot axis (A1′) passing through the center of thejoint and being substantially oblique to the first rotation axis (X1),the second triad second shaft yoke being pivotally mounted on the secondshaft with the respective second shaft second pivot axis (A2′) passingthrough the center of the joint and being substantially oblique to thesecond rotation axis (X2), the angle between the first shaft secondpivot axis (A1′) and the first rotation axis (X1) equals the anglebetween the second shaft second pivot axis (A2′) and the second rotationaxis (X2), the three yokes of the second triad of yokes are pivotallymounted to each other to pivot about a second common axis (C′) passingthough the center of the joint; the third triad of yokes comprising athird triad control yoke, a third triad first shaft yoke and a thirdtriad second shaft yoke, the third triad first shaft yoke beingpivotally mounted on the first shaft with the respective first shaftthird pivot axis (A1″) passing through the center of the joint and beingsubstantially oblique to the first rotation axis (X1), the third triadsecond shaft yoke being pivotally mounted on the second shaft with therespective second shaft third pivot axis (A2″) passing through thecenter of the joint and being substantially oblique to the secondrotation axis (X2), the angle between the first shaft third pivot axis(A1″) and the first rotation axis (X1) equals the angle between thesecond shaft third pivot axis (A2″) and the second rotation axis (X2),the three yokes of the third triad of yokes are pivotally mounted toeach other to pivot about a third common axis (C″) passing though thecenter of the joint; the first triad control yoke, the second triadcontrol yoke and the third triad control yoke are pivotally mounted toeach other to pivot about a common axis (Z) perpendicular to the firstcommon axis (C), to the second common axis (C′) and to the third commonaxis (C″) at the center of the joint, the control yokes of the threetriads are crosses, the rest yokes of the three triads are forks.
 5. Aconstant velocity joint according claim 1 wherein: said set ofadditional pivotally mounted yokes is a spherical pantograph mechanismpivotally mounted at one end on an oblique pin of the first shaft,pivotally mounted at its other end on an oblique pin of the secondshaft, the control yoke is pivotally supported by the central hub of thespherical pantograph mechanism.
 6. A constant velocity joint comprisingat least: a first shaft rotating about a first rotation axis (X1); asecond shaft rotating about a second rotation axis (X2), the firstrotation axis (X1) and the second rotation axis (X2) intersect at thecenter of the joint which is a point fixed relative to the first andsecond shafts; the first shaft yoke being pivotally mounted on the firstshaft with the respective first pivot axis (A1) passing through thecenter of the joint, the first pivot axis (A1) is near, but not exactly,perpendicular to the first rotation axis (X1), the second shaft yokebeing pivotally mounted on the second shaft with the respective secondpivot axis (A2) passing through the center of the joint, the anglebetween the first pivot axis (A1) and the first rotation axis (X1)equals to the angle between the second pivot axis (A2) and the secondrotation axis (X2), the three yokes of the triad of yokes are pivotallymounted to each other to pivot about a common axis passing though thecenter of the joint; a set of auxiliary yokes, the set of auxiliaryyokes constitutes a spherical pantograph mechanism, the one end of thespherical pantograph mechanism is pivotally mounted on an oblique pin ofthe first shaft, the other end of the spherical pantograph mechanism ispivotally mounted on an oblique pin of the second shaft, the controlyoke is pivotally supported at the center of the spherical pantographmechanism.
 7. A constant velocity joint according claim 6, wherein: thefirst pivot axis (A1) is more than 0.5 degrees offset from beingperpendicular to the first rotation axis (X1).
 8. A constant velocityjoint according claim 6, wherein: the first pivot axis (A1) is more thanone degree offset from being perpendicular to the first rotation axis(X1).
 9. A constant velocity joint according claim 6, wherein: the anglebetween the first pivot axis (A1) and the first rotation axis (X1) isbetween 89.5 and 85 degrees.
 10. A constant velocity joint accordingclaim 6, wherein: the angle between the first pivot axis (A1) and thefirst rotation axis (X1) is between 89 and 80 degrees.